Uniflow steam engine



B. V. NORDBERG.

UNIFLOW STEAM ENGINE.

APPLICATION FILED JULY 7,1917.

Patented Mar. 14, 1922.

2 SHEETS-SHEET 1- B. V. NORDBERG.

UNIFLOW STEAM ENGINE.

APPLECATION FILED JULY 7.19 7.

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BRUNO V. NORDBERG, 0F MILWAUKEE, WISCONSIN.

UNIFLOW STEAM ENGINE.

Application filed July 7,

To all whom it may concern:

Be it known that I, BRUNO V.- NORDBERG, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented certain new and useful Improvements in Unifiow Steam Engines, of which the following is a specification, reference being had to the accompanying drawing, forming a part thereof.

This invention relates to steam engines, single or double, acting, in which the flow of steam through either end of the cylinder is in one direction only.

The main objects of the invention are to prevent dissipation and wasteof the heat developed by compression and consequent reduction in economy,and generally to increase the efliciency' and improve the construction and operation of engines of this class.

It consists in the construction, arrangement and combination of parts as hereinafter particularly described and pointed out in the claims.

In the accompanying drawing like characters designate the same parts in both figures.

Figure 1 is a central longitudinal section on the line 11, Fig. 2, of a double acting uniflow engine embodying the invention. and Fig. 2 is a cross section thereof on the line 22, Fig. 1.

This invention is based upon the discovery that in unifiow steam engines, in which the steam on the return stroke of the piston is compressed to or nearly to boiler pressure, the final temperature developed by compression is considerably higher than the temperature of the working steam. This is particularly the case when a high steam pressure is maintained on the engine and when the piston stroke of the engine is comparatively long.

In engines of this kind, where the exhaust takes place at the end of the working stroke and for about ten per cent of the working stroke and ten per cent of the return stroke a layer of wet steam apparently follows the piston and is exhausted from the cylinder during the first part of the period during which the exhaust port is open, comparatively dry steam is exhausted during the latter part of this period.- The cylinder is thus left full of comparatively dry steam at the polnt of closure of the exhaust port, and, since the ratio of compression of said Specification of Letters Patent.

Patented Mar. 14, 1922.

1917. Serial No. 179,181.

steam is very high and consequently the increase of temperature due to such compresslon is also great, a high temperature is obtained at the end of the compression period, which, according to observations made, may reach 600 degrees Fahr. and over, while the temperature of the working steam, even if superheated, is below 600 degrees.

Under these conditions the ordinary method of heating the cylinder head, which vmethod is beneficial with respect to steam economy under ordinary conditions where a comparatively low degree of compression takes place, would of course be detrimental under the first mentioned conditions, since, instead of heat being transmitted from the heated cylinder head into the cylinder at the beginning of the working stroke of the piston, the excessive heat of compression would cause a flow of heat from the cylinder outward, which would tend to dissipate the heat and reduce the economy of the engine.

To prevent this dissipation and loss of heat developed by compression, and consequent reduction in economy of steam and efiiciency in the operation of the engine, in accordance with the present invention, the engine is constructed substantially as shown by the drawing, in which a designates the cylinder of a double acting uniflow engine formed adjacent to its ends with steam admission ports I) and midway between them with an exhaust port or circumferential series of exhaust ports 0, opening into a belt or passage d, which surrounds the cylinder and with which the exhaust pipe e is connected. I

The cylinder heads f and g, which are fitted and secured in the ends of the cylinder, are preferably made hollow and form vacuum insulating chambers h, which are connected by pipes i with a pump or other means for maintaining a vacuum in said chambers, to prevent conduction of heat from the inside to the outside of the cylinder.

The inner surfaces of the heads are covered by layers 3' of insulating or nonheat-conducting material such asasbestos board, and this material is protected and held in place by retaining plates is of steel or other strong material,. fastened to the heads as shown, by screws or other suitable means.- The exposed inner faces of these retaining plates are polished bright or plated, so as to reflect heat.

The end faces of the piston Z, which in the type of engine corresponds approximately in length with the distance between the ad-, mission and exhaust ports ,and uncovers the exhaust port at the ends of the working strokes of the piston, are preferably, like the inner surfaces of the cylinder heads, covered by layers m-of insulating or non-heatconducting material, protected and held in place by plates n, having outer bright polished or plated heat reflecting surfaces.

The admission of steam into the ends of the cylinder through the ports 7) next to the heads f, is controlled by valves 0, which may be of the usual or any suitable construction.

In the operation of the engine constructed as shown and described, during each return stroke of the piston Z, the steam in the cylinder (1 is compressed from an initial volume of about nine-tenths of the total volume of the cylinder, to a final volume equal to the clearance space, which is so proportioned that the final pressure of compression is nearly equal to the boiler pressure. The compressed steam will then have a considerably higher temperature than the working steam from the boiler. Working steam from the boiler is admitted to the cylinder at points near the dead centers of the engine, and mingles with the compressed steam in the clearance spaces, whereby either the temperature of the mixture is raised above the initial temperature of the working steam if the working steam is initially dry or superheated, or if such steam is moist, its moisture will be evaporated by the heat of the compressed steam in the clearance spaces. In either case, during the forward or expansion strokes of the piston the steam performs its work without dissipation and loss of the heat produced by the compression of the steam in the cylinder.

In practice it has been found of greater advantage to cover and protect the inner surfaces of the cylinder heads than to cover and protect the end surface of the piston, so that the insulation may be omitted from the piston.

For the sake of convenience, the steam admission ports and valves may be located in the cylinder heads in the usual manner, but more perfect insulation can be obtained if they are located as shown and described, in the'body of the cylinder adjacent to the heads, which may then present uninterrupted or plain inner surfaces within the cylinder.

For a single acting engine of this type it is obvious that but one cylinder head and one end of the piston would be provided with insulation and heat reflecting retainingrplates.

arious changes in the minor details of construction and arrangement of parts may be made without materially affecting the operation of the engine and without departure from the principle of the invention as defined in the following claims.

I claim:

1. In a uniflow steam engine the combination of a cylinder having separate steam admission and exhaust ports and a head adjacent the admission port, a piston corresponding in length approximately with the distance between the admission and exhaust ports and adapted to uncover the exhaust port at the end of the working stroke of the piston, a layer of non-heat-conducting material covering the inner surface of said cylinder head, and a metal retaining plate secured to the head over said non-heat-conducting material.

2. In a uniflow steam engine the combination of a cylinder having separate steam admission and exhaust ports and a head adjacent the admission port, a piston corresponding in length approximately with the distance between the admission and exhaust ports and adapted to uncover the exhaust port at the end of the working stroke of the piston, a layer of non-heat-conducting material covering the inner surface of said cylinder head, and a metal retaining plate secured to the head over said non-heat-conducting material and having an inner heat reflecting surface.

3. In a uniflow steam engine the combination of a cylinder having separate steam admission and exhaust ports, a piston corresponding in length with the distance between the admission and exhaust ports and adapted to uncover the exhaust port at the end of the working stroke of the piston, a hollow cylinder head forming a vacuum insulation chamber adjacent the admission port, an air exhausting connection with said chamber, a layer of non-heat-conducting material covering the inner surface of the head, and a metal retaining plate secured to the head over said non-heat-conducting material.

4. In a uniflow steam engine the combination of a cylinder having separate steam admission and exhaust ports, a piston corresponding in length approximately with the distance between the admission and exhaust ports and adapted to uncover the exhaust port at the end of the working stroke of the piston, a, hollow cylinder head forming a vacuum insulating chamber adjacent the-admission port, an air exhausting connection with said chamber, a layer of non-heat-conducting material covering the inner surface of the head, and a metal retaining plate secured to the head over said non-heat-conducting material and having an inner heat reflecting surface.

5. In a uniflow steam engine the combination of a cylinder having separate steam admission and exhaust ports, a piston corresponding in length with the distance -between said ports and adapted to uncover the exhaust port at the end of the working stroke of the piston, heat insulating material covering the inner surface of the cylinder head adjacent the admission port and the opposing end of the piston, and metal retaining plates secured to the cylinder head and piston over said insulating material.

6. In a unflow steam engine the combination of a cylinder having separate steam admission and exhaust ports, a piston corresponding in length with the distance between said ports and adapted to uncover the exhaust port at the end of the working stroke of the piston, heat insulating material covering the inner surface of the cylinder head adjacent the admission port and the opposing end of the piston, metal retaining plates secured to the cylinder head and piston over said insulating material and having inner heat reflecting surfaces. 7. In a uniflow steam engine the combination of a cylinder having separate steam admission and exhaust ports, a piston corresponding in length approximately with the distance between said ports and adapted to uncover the exhaust 'portat the end of the working stroke of the piston, a hollow cylinder head forming a vacuum insulation chamber adj went the admission port, an air exhausting connection with said chamber, heat insulating material covering the inner surface of said cylinder head and the opposing end of the piston, and metal retaining plates covering the insulating material.

8. In a uniflow steam engine the combination of a cylinder having separate steam admission and' exhaust ports, a piston corresponding in length approxnnately with the distance between said ports and a'da ted to uncover the exhaust port at the en of the working stroke of the piston, a hollow c linder head forming a vacuum insulation chamber adjacent the admission port, an air exhaustin connection with said chamber, heat insu ating material covering the inner surface of said cylinder head and the opposing end of the piston, and metal retaining plates secured to the cylinder head and piston over said insulating material and having inner heat reflecting surfaces. A

In witness whereof I hereunto afiix my signature.

BRUNO V. NORDBERG. 

